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  Copyright (c) 2017-2018 Jean-Marc VIGLINO,
  released under CeCILL-B (french BSD like) licence: http://www.cecill.info/
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  <title>ol-ext: HexBin source</title>
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  <meta name="description" content="ol.source.HexBin is a source to display hexagonal binning on a map." />
  <meta name="keywords" content="ol3, layer, hexbin, cluster, hexagon, binning, heatmap" />

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  <style>
    input {
      vertical-align: middle;
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    #legend{
      background: #fff;
      padding: 0.5em 1em;
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    #legend li
    {	padding-left: 0.5em;
    }
    #legend li:first-child
    {	padding: 0 0 0.5em;
    }
    .legend{
      display: inline-block;
      width: 2em;
      height: 1.5em;
      vertical-align: middle;
      background-color: orange;
    }
    .legend.mini
    {	background-color: green;
    }
    .legend.maxi
    {	background-color: #800;
    }
    .gradient .legend
    {	background-color: rgba(0,0,255, 0.25);
    }
    .gradient .legend.mini
    {	background-color: rgba(0,0,255, 0.05);
    }
    .gradient .legend.maxi
    {	background-color: rgba(0,0,255, 0.5);
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      position: absolute;
      border-color: rgba(0,0,255,0.5) transparent;
      border-width: 0.5em 1em;
      border-style: solid;
    }
    .point .legend:before 
    {	top: 100%;
      border-bottom: 0;
    }
    .point .legend:after
    {	bottom: 100%;
      border-top: 0;
    }
    .point .legend.mini
    {	transform: scale(0.2);
    }
    .point .legend.maxi
    {	transform: scale(0.7);
    }

    #map {
      width: 600px;
      height: 400px;
    }
    .fullscreen #map {
      position: fixed;
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      padding: .2em 1em;
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</head>
<body >
  <a href="https://github.com/Viglino/ol-ext" class="icss-github-corner"><i></i></a>

  <a href="../../index.html">
    <h1>ol-ext: HexBin source</h1>
  </a>

  <div class="info">
    Hexagonal binning is a convenient way for aggregating data into a coarser representation for display.
    <br/>
    In an hexbin map (hexagonal heatmap) features are scattered on hexagons.
    <br/>
    Hexbins can support a color encoding or point encoding. 
    You can use the color, density of the hexagon or its size to display 
    the value of the features aggregated in the hexagon.
    <ul>
      <li>
        <i>ol.source.HexBin</i> is a ol.source.Vector, similar to a ol.source.Cluster
      </li>
      <li>
        <i>ol.source.ImageHexBin</i> is a ol.source.ImageVector, more efficient to use with large data sets.
      </li>
      <li>
        HexBin use a <i>ol.HexGrid</i> to compute hexagonal grid. 
        <br/>
        For more information on hexgrid metrics, see
        <a href="https://viglino.github.io/ol-games/examples/map.hexmap.html">the Hexmap example</a>.
      </li>
    </ul>
  </div>

  <!-- Map DIV -->
  <div id="map"></div>

  <div class="options">
    <i class="fa fa-arrows-alt"  title="fullscreen" onclick="$('body').toggleClass('fullscreen'); map.updateSize();"></i>
    <h2>Options:</h2>
    <ul>
      <li>
        Hexagon size: <input id="size" type="range" min="1000" max="300000" value="100000" onchange="reset();" step="1000" />
        <button onclick="$('#size').attr('type')==='range' ? $('#size').attr('type','number') : $('#size').attr('type','range');">
          <i class="fa fa-keyboard-o"></i> slide/number
        </button>
      </li>
      <li>
        Style:
        <select id="style" onchange="hexbin.changed(); $('#legend').removeClass().addClass($(this).val())">
          <option value="color">Color</option>
          <option value="gradient">Gradient</option>
          <option value="point">Point</option>
        </select>
      </li>
      <li>
        <input id="image" type="checkbox" checked="checked" onchange="reset()"/><label for="image"> layer image</label>
      </li>
      <li>
          <div class="info">
              <input id="showsource" type="checkbox" onchange="layerSource.setVisible($(this).prop('checked')); modify.setActive($(this).prop('checked'));" /><label for="showsource">
                  Display source features and move them around to see what happens to the bin!
              </label>
          </div>
      </li>
      <li>
        <button onclick='save()'><i class="fa fa-download"></i> download result</button>
      </li>
    </ul>
    <div>
      <ul id="legend">
        <li>
          Legend:
        </li>
        <li>
          <div class="legend mini"></div>
          <span class="min"></span>-
        </li>
        <li>
          <div class="legend"></div>
          <span class="min"></span> - <span class="max"></span>
        </li>
        <li>
          <div class="legend maxi"></div>
          <span class="max"></span>+
        </li>
      </ul>
    </div>
    <div class="info">Selection: <span>0</span> feature(s)</div>
    <div class="info">
      <i class="fa fa-upload"></i> Drag'n'drop .geojson to calculate on your data!
      <br/>
      <label>
        <input id="add" type="checkbox" />
        add features when dropped
      </label>
    </div>
  </div>

<script type="text/javascript">
  // The map
  var map = new ol.Map({
    target: 'map',
    view: new ol.View({
      zoom: 4,
      center: [166326, 5992663]
    }),
    layers: [ new ol.layer.Tile({ source: new ol.source.OSM() })]
  });

  var select  = new ol.interaction.Select();
  map.addInteraction(select);
  select.on('select', function(e){
    if (e.selected.length){
      var f = e.selected[0].get('features');
      if (f) $(".options .info span").text(e.selected[0].get('features').length);
      else $(".options .info span").text("0");
    }
    else $(".options .info span").text("0");
  });

  // Create a set of features on seed points
  function addFeatures(nb){
    var ssize = 20;		// seed size
    var ext = map.getView().calculateExtent(map.getSize());
    var dx = ext[2]-ext[0];
    var dy = ext[3]-ext[1];
    var dl = Math.min(dx,dy);
    var features=[];
    for (var i=0; i<nb/ssize; ++i){
      var seed = [ext[0]+dx*Math.random(), ext[1]+dy*Math.random()]
      for (var j=0; j<ssize; j++){
        var f = new ol.Feature(new ol.geom.Point([
          seed[0] + dl/10*Math.random(),
          seed[1] + dl/10*Math.random()
        ]));
        f.set('id',i*ssize+j);
        features.push(f);
      }
    }
    source.clear(true);
    source.addFeatures(features);
  }

  // Vector source
  var source = new ol.source.Vector();
  // add 2000 features
  addFeatures(2000);
  // Interaction to move the source features
  var modify = new ol.interaction.Modify({ source: source });
  modify.setActive(false);
  map.addInteraction(modify);
  var layerSource = new ol.layer.Vector({ source: source, visible:false })
  map.addLayer(layerSource);

  var hexbin, layer, binSize;
  var style = $("#style");
  var min, max, maxi;
  var minRadius = 1;
  var styleFn = function(f,res){
    switch (style.val()){
      // Display a point with a radius 
      // depending on the number of objects in the aggregate.
      case 'point':{
        var radius = Math.round(binSize/res +0.5) * Math.min(1,f.get('features').length/max);
        if (radius < minRadius) radius = minRadius;
        return	[ new ol.style.Style({
          image: new ol.style.RegularShape({
            points: 6,
              radius: radius,
              fill: new ol.style.Fill({ color: [0,0,255] }),
              rotateWithView: true
            }),
            geometry: new ol.geom.Point(f.get('center'))
          })
          //, new ol.style.Style({ fill: new ol.style.Fill({color: [0,0,255,.1] }) })
        ];
      }
      // Display the polygon with a gradient value (opacity) 
      // depending on the number of objects in the aggregate.
      case 'gradient': {
        var opacity = Math.min(1,f.get('features').length/max);
        return [ new ol.style.Style({ fill: new ol.style.Fill({ color: [0,0,255,opacity] }) }) ];
      }
      // Display the polygon with a color
      // depending on the number of objects in the aggregate.
      case 'color':
      default: {
        var color;
        if (f.get('features').length > max) color = [136, 0, 0, 1];
        else if (f.get('features').length > min) color = [255, 165, 0, 1];
        else color = [0, 136, 0, 1];
        return [ new ol.style.Style({ fill: new ol.style.Fill({  color: color }) }) ];
      }
    }
  };
  
  // Create HexBin and calculate min/max
  function reset() {
    var size = Number($('#size').val());
    if (layer) map.removeLayer(layer);
    binSize = size;
    var features;
    hexbin = new ol.source.HexBin({
      source: source,		// source of the bin
      size: size			// hexagon size (in map unit)
    });
    layer = new ol.layer.Vector({ 
      source: hexbin, 
      opacity:0.5, 
      style: styleFn, 
      renderMode: $("#image").prop('checked')?'image':'vector' 
    });
    features = hexbin.getFeatures();
    // Calculate min/ max value
    min = Infinity;
    max = 0;
    for (var i=0, f; f=features[i]; i++)
    {	var n = f.get('features').length;
      if (n<min) min = n;
      if (n>max) max = n;
    }
    var dl = (max-min);
    maxi = max;
    min = Math.max(1,Math.round(dl/4));
    max = Math.round(max - dl/3);
    $(".min").text(min);
    $(".max").text(max);

    // Add layer
    map.addLayer(layer);
  }
  reset (Number($("#size").val()));

  // Add feature on drop
  var dd = new ol.interaction.DropFile();
  map.addInteraction (dd);
  dd.on('loadstart', function () { $('body').addClass('waiting'); });
  dd.on('loadend', function () { $('body').removeClass('waiting'); });
	dd.on ('addfeatures', function(event) {
    var f = event.features;
    if (!$("#add").prop('checked')) {
      source.clear(true);
    }
    source.addFeatures(f);
  });

  // Save
  function save () {
    var format = new ol.format.GeoJSON();
    var hexa = layer.getSource().getHexFeatures();
    if (style.val()==='point'){
      var size = hexa[0].getGeometry().getExtent();
      size = map.getView().getResolution() / (size[2]-size[0]) ;
      var minVal = minRadius * size;
      console.log(minVal)
      hexa.forEach(function(f){
        var radius = Math.min(1,f.get('nb')/max);
        if (radius < minVal) {
          console.log(radius, minVal)
          radius = minVal;
        }
        var geom = f.getGeometry().getCoordinates()[0];
        var center = ol.extent.getCenter(f.getGeometry().getExtent());
        geom.forEach(function(p) {
          p[0] = center[0] + (p[0]-center[0])*radius;
          p[1] = center[1] + (p[1]-center[1])*radius;
        });
        f.setGeometry(new ol.geom.Polygon([geom]));
      });
    }
		var data = format.writeFeatures(hexa, {
			dataProjection: 'EPSG:4326',
			featureProjection: map.getView().getProjection()
    });
		var blob = new Blob([data], {type: "text/plain;charset=utf-8"});
		saveAs(blob, "hexmap.geojson");
	}

</script>

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